NPT & ORB Ports and Fittings for Hydraulic Cylinders | Cylinder Repair Components, Inc.

Ports and Fittings

NPT (National Pipe Tapered) threaded fittings seal by means of an interference fit between the male and female threads, and two fittings should screw in only partway before jamming.

NPT fitting sizes refer to the nominal ID of a standard pipe. This is where the confusion comes in. Most fittings are named for the thread size, but NPT sizes are not. An NPT fitting measuring 3/8" OD thread is actually a 1/8 NPT, not 3/8 NPT. Use the chart below to identify NPT fitting sizes.

Unlike NPT threaded fittings seals on a metal-to-metal flare, the ORB seals on an O-ring. This type of seal offers the best leak free connection, even if small nicks and dings are found on the sealing surfaces of the ports. This O-ring connection is highly recommended for medium and high pressure systems, and is excellent in vibration and/or temperature cycling environments.

NPT Ports
National Pipe Thread Ports
SizePSI
1/8" - NPT 3000
1/4" - NPT 3000
3/8" - NPT 3000
1/2" - NPT 3000
3/4" - NPT 3000
1" - NPT 3000
ORB Ports
O-Ring Boss Ports
SizePSI
#4 (7/16-20) 3000
#6 (9/16-18) 3000
#8 (3/4-16) 3000
#10 (7/8-14) 3000
#12 (1 1/16-12) 3000
#16 (1 5/6-12) 3000
#24 (1 7/8-12) 3000
NPT Coupling
National Pipe Thread Coupling
SizePSI
1/4" - NPT 3000
3/8" - NPT 3000
1/2" - NPT 3000
3/4" - NPT 3000
1" - NPT 3000
NPT Elbow
National Pipe Thread Elbow
SizePSI
1/4" - NPT 3000
3/8" - NPT 3000
1/2" - NPT 3000
3/4" - NPT 3000
1" - NPT 3000
NPT Tee
National Pipe Thread Tee
SizePSI
3/8" - NPT 3000
1/2" - NPT 3000
3/4" - NPT 3000
1" - NPT 3000
ORB Elbow Ports
SizePSI
ORB 90 - #4 3000
ORB 90 - #6 3000
ORB 90 - #8 3000
ORB 90 - #10 3000
ORB 90 - #12 3000
ORB 90 - #16 3000

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